摩訶止觀 5.135

5.135

觀者，觀察無明之心，上等於法性，本來皆空；下等一切妄想善惡，皆如虛空，無二無別。譬如劫盡，從地上至初禪，炎炎無非是火。又如虛空藏菩薩所現之相，一切皆空。如海慧初來，所現一切皆水。介爾念起，所念、念者無不即空；空亦不可得。如前火木能使薪然，亦復自然。法界洞朗，咸皆大明，名之為「觀」。

As for 'contemplation', it is to observe that the mind of avidyā, above, is equal to dharmatā and originally empty; below, it is equal to all false thoughts, good and bad, which are all like empty space, without duality or distinction. For example, at the end of a kalpa, from the ground up to the first dhyāna, everything blazing is nothing but fire. It is also like the signs manifested by Bodhisattva Ākāśagarbha, where everything is empty space; or like when Sāgaramati first arrived, where everything manifested was water. When the slightest thought arises, that which is thought and the thinker are both nothing other than empty; emptiness is also unobtainable. Just as the aforementioned fire-producing wood can cause the fuel to burn, it is also spontaneous. The dharmadhātu is thoroughly clear and all is greatly illuminated; this is called 'contemplation'.